1. Field of this Invention
This invention relates to a polyethylene terephthalate (hereafter “PET”) copolyester composition used to manufacture polyester bottles of different sizes ranging from volumes of 10 liters and up to 5 gallons. Specifically, this invention relates to a PET copolyester composition used to manufacture bottle embryos with weight greater than 600 grams and thickness greater than 7.0 millimeters and containers with an inner volume greater than liters.
2. Description of Related Prior Art
Bulk water market has been expanding gradually as the public pays more attention to the quality of drinking water. Many public sites and business offices now provide distilled water contained in 5-gallon containers for drinking. Traditionally, bulk water containers have been made from polyvinyl chloride (PVC) or polycarbonate (PC) material. Although it is cheaper to use PVC due to environmental concerns the use of this material has declined considerably. Similarly, although containers made of PC have excellent qualities the material cost is considerably expensive.
The use of PET copolyester material presents a promising solution, although present prior art compositions used have resulted in products with numerous quality problems. Prior art PET copolyester compositions used to manufacture bottles for carbonic acid beverages, mineral water or tea beverages usually contain 0-3 mole % of isophthalic acid (hereafter “IPA”) based on the total weight of the copolyester or 1.5-4.0 mole % of diethylene glycol (hereafter “DEG”) based on the total weight of the copolyester. These composition range ratios, which results in the easy crystallization of the copolyester material during the inject-stretch-blow-molding process, are suitable for manufacturing embryos with thickness of between 3-4 mm and maximum weight of between 100-120 grams, and are suitable for manufacturing bottles with an inner volume of less than 5 liters. However, when the same composition range ratios are used to manufacture bottle embryos with thickness greater than 7 mm and weight greater than 600 grams the bottle embryos are covered with crystalline haze, which causes instability during the inject-stretch-blow-molding process. To prevent the hazing effect, the prior art teaches extending the cooling time of the bottle embryos which is uneconomical and lowers overall productivity.
Attempting to solve the problem of hazing and extension of bottle embryos cooling time, U.S. Pat. No. 6,309,718B1 teaches using a copolyester composition which produces bottle embryos having weight greater than 200 grams and manufactured bottles with an inner volume of several gallons. The copolyester composition taught by the aforementioned patent contains 4-10 mole % of cyclohexane dimethanol or 6-17 mole % of isophthalic acid or a combination of both compounds, dicarboxylic acid compound such as 2,6-naphthalene dicarboxylic acid with a maximum mole % of 50 and an intrinsic viscosity of between 0.75-0.85 dl/g.